The present invention relates to a steerable drive shaft for motor vehicles equipped with wheels each driven by a double-universal joint.
With heretofore known constructions of vehicles having front-wheel drive or four-wheel drive (all-wheel drive), the drive of the wheels is accomplished from an axle drive shaft, both ends of which are connected with the double-universal joints. Since, however, the angular position between the drive shaft and the power-takeoff shaft of a universal joint is only possible up to a certain degree, because otherwise the universal joint will become overloaded or damaged, limits are set for the steering deflection or turning of the wheels when using a steerable drive shaft of this type.
In the case of vehicles where the front axle is not driven it has already been possible to obtain extremely small turning circles or radii and thus an extremely favorable maneuverability of the vehicle. This is especially desirable for tractors. However when the front axle or shaft is driven difficulties exist in attaining such small turning circles, for the above mentioned reasons.
In order to obtain as large as possible deflection or turning angles at a steerable drive shaft for motor vehicles having wheels driven by an axle drive shaft through the agency of a respective double-universal joint, it has already been proposed to incorporate in each case between the double-universal joint and the axle drive shaft a further single-universal joint and to connect such via a connection shaft with the double-universal joint, and each connection shaft encloses an angle with the axle drive shaft. The entire arrangment is carried out such that the angular disposition of both double-universal joints remains the same notwithstanding the different size deflection or turning angles of the wheels. In this regard it is to be appreciated that with larger turning or steering deflections, especially in the case of vehicles having a small spacing between the axles, such as encountered with tractors, the wheel located at the inside of the curve must be turned much more intensely than the wheel located at the outside of the curve, and while otherwise the double-universal joint located at the inside of the curve would limit the steering deflection, it was possible with this proposed construction to achieve the result that the angular disposition of the double-universal joint located at the inside of the curve is smaller in relation to the turning angle of the wheel by the aforementioned angle, which the axle drive shaft and the connection shaft enclose with one another, and the angular position of the double-universal joint located at the outside of the curve is larger by the mentioned angle in relation to the turning or deflection angle of the wheel, so that there can be completely utilized the previously mentioned limited angular positioning of both double-universal joints.
Yet, the previously described prior art construction, in contrast to the former conventional steerable drive shafts, requires the installation of two further universal joints. This considerably increases the cost of the construction, because the axle drive shaft must be divided and connected with flanges in order to install them in the axle housing and to be able to connect them with the centrally located differential.